[Characteristics of thiamine triphosphatase from neural cells plasma membranes]

The kinetic parameters of the ThTP hydrolysis by synaptic plasma membranes isolated from rat brain were investigated. It was shown that the ThTPase reaction pH optimum was 7.4, the apparent K(m) was 52 microM and the apparent affinity constant for Mg2+ was 1.9 mM. The comparative analysis of the indicated parameters was done for the ThTPase activity of membrane bound (the data of present work and literature data) and cytosolic (literature data) proteins. The analysis allows us to suppose that thiamine-binding protein described earlier is the single ThTPase activity carrier in neural cells plasma membranes. It was shown that the active site of the enzyme that catalyzes the ThTP hydrolysis in neural cells plasma membranes is associated with the inside membrane surface.